This section provides background information related to the present disclosure which is not necessarily prior art. This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
This device applies the microsublimation technique to achieve highly precise and accurate boron isotopic analysis for small samples (boron<1 ng). We have developed a microsublimation method to process more samples (up to 20 per hotplate) with excellent reproducibility.
The microsublimation technique for boron purification is based on the tendency of boron to sublimate at a temperature and pressure that alkaline matrices and organic matter remain in solution or solid form. The technique design utilized uses a 5 mL conic bottom Savillex PFA vial. The vial is set upside-down so that the cap can be heated, causing the boron to sublimate and then condense onto a cooler surface at the conical point in the bottom of the vial. In previous experiments, the flat bottom, the cap of the vial, was heated to 60-65° C. for 12 hours with aluminum foil wrapped on the lower part of the savillex. The drawback of this design results from the difficulty of controlling and maintaining stable and consistent heating and cooling conditions. Non-reproducible heating and cooling conditions may result in variable sample recoveries. An additional fan for cooling still leads to inconsistent heating conditions between different vials, especially at the conical top of the vials. Therefore, we designed and fabricated water-cooled microsublimation block sets to ensure that all samples are exposed to the same thermal conditions.
Machined heating and cooling blocks are coated in a thermoplastic. The bottom heating blocks were machined to precisely fit the tops of the 5 mL conic beakers. Water from the in-house deionized chilled water system flows through the upper part of cooling coil block through machined channels connected by polyvinyl chloride (PVC) tubing. The cooling coil block rests on threaded chlorinated polyvinyl chloride (CPVC), such that no vibration from water flow disturbs the drops. In addition to supporting cooling block, the low thermal conductivity CPVC prevents heat transfer to the upper cooling block, is corrosion resistant, and can withstand temperatures up to 90° C. The coated stainless steel design of our heating blocks provides a uniform heating and cooling surfaces for the sublimation, which facilitates complete boron evaporation. In order to process large numbers of samples, we designed the heating and cooling blocks to process 10 separate samples at a time and up to 20 per hotplate.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
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